The remarks, which Najib made at the opening ceremony of China-Malaysia Economic Summit, not only concluded his trip to China, but also further cemented the four-decade relationship between the two countries.

On Saturday, the sides signed a joint communique to mark the 40th anniversary of diplomatic ties. The two sides pledged to carry forward their links to achieve a targeted trade volume of US$160 billion in 2017.

They also agreed to upgrade economic and financial cooperation, especially in the production of halal food, water processing and railway construction.

The signing ceremony took place in the West Lobby of the Great Hall of the People in Beijing, the same place where Najib's father - the then-Prime Minister Adbul Razak - led an ice-breaking trip to Beijing to establish diplomatic relations in 1974.

"Sino-Malaysian relations have grown into a towering tree over the four decades, and will blossom and bear fruit in the future," Premier Li Keqiang said upon signing the communique.

"Like all friendships, ours is testing sometimes," Najib said, acknowledging that the search for the missing flight MH370 has been a frustrating time.

However, he said he believed the two nations will become even closer through the tragedy, because "true friendship becomes a supporting force for each other in times of difficulties".

Najib promised to continue the search for the flight, which went missing on March 8 with 154 Chinese passengers on broad.

China has been Malaysia's largest trading partner for five consecutive years, with the volume of bilateral trade reaching more than $106 billion in 2013.

Malaysia is China's biggest trading partner among the 10-member Association of Southeast Asian Nations, and the third country in Asia to have an annual trade volume with China of US$100 billion, after Japan and South Korea.